Over the years since 9/11, there have been many calls for systematic analysis of domestic counterterrorism expenditures—indeed, in the United States, it is required by current regulations. The paper lays out and explains the standard cost/benefit and risk-analytic approaches that might be applied to evaluate such expenditures. However, such research has been quite limited so far. While systematic analysis can make the counterterrorism enterprise more coherent and efficient, domestic terrorism in most countries (particularly those outside of war zones) scarcely presents enough of a hazard to justify the enormous efforts and expenditures that have been made to counter it. It is an area of research that should be more fully developed.

The primary conceptual underpinning of understanding offender decision making is that they are rational actors. This chapter applies rational-choice approaches that are used to understand everyday criminals to the problem of lone-actor terrorism. The first section poses the question: who are the lone actor terrorists? It is established that they are a broad set of individuals; no profile exists, and they are varied in terms traits and pathways into terrorism. The second section discusses the rationality of lone actor terrorists in terms of the decision-making processes surrounding choosing a target and hostile reconnaissance. Decisions about when, where, and how to carry out a particular attack derive from simple cost-benefit analyses, including anticipated and unexpected costs. The next section discusses how cost-benefit analyses can be used to disrupt lone-actor terrorism through detection and deterrence. The final section consists of several illustrative examples. This is followed by suggestions of basic prevention mechanisms to counter lone-actor terrorism based on the situational qualities of their behaviour.